Conventional heater cores are produced by soldering side tanks or manifolds to a core element comprised of, a succession of juxtaposed corrugated fin units which are joined together and define respective air and liquid passages. The liquid passages are connected to the side tanks for circulation of the liquid through the liquid passages where the liquid undergoes heat exchange with air passing through the air passages. In the course of manufacture, the exposed surfaces of the heater core are normally covered with flux and solder leading to objectionable discoloration of the heater core.
Various attempts have been made to remove the flux and solder deposits but none have proved successful, especially in mass production at a high volume or capacity.
Attempts have been made to clean the flux and solder impurities from the exposed surfaces of the heater cores by air blasting a dry sand mixture against the heater cores; this has proved to be unsuccessful because of the excessive dust which is produced and particularly because the dust contains particles of lead from the solder. The creation of such a pollutant atmosphere is unacceptable in the workplace.
Other methods of treatment of the heater cores have involved chemical treatment by immersion of the cores into a chemical treatment bath. This has a number of disadvantages, including the maintenance of such a bath and the inability to provide a high capacity treatment process.
Another method of treating the exposed surfaces of the heater cores involves painting the surfaces to conceal the flux and solder deposits. Such a process is expensive, is difficult to achieve on a mass production basis and involves dispersal of harmful ingredients into the atmosphere.
It is known to clean articles, to remove grease, scales, burrs, dirt, rust and surface contaminants by a wet blasting treatment in which abrasive particles are contained in a liquid. Such wet blasting treatments have the advantage of eliminating dust and permitting finer abrasive particles to be used as compared to the use of abrasive particles in a dry blasting operation.
The conventional wet blasting techniques are not compatible with high capacity treatment of heater cores on a mass production basis. Furthermore, the wet blast liquid leaves a residue of abrasive particles on the treated workpieces which although acceptable in other uses is not desirable in the case of heater cores.